Is this tool really free?

Yes, 100% free with no limits, no signup, and no watermarks.

Does my file get uploaded to a server?

No. Everything runs locally in your browser — your file never leaves your device.

Subtitles embedded in MKV are generally not remuxed; the video and audio tracks are converted.

MKV to MP4 runs entirely in your browser. Enable JavaScript to use the interactive tool — your files are processed locally and never uploaded.

MKV to MP4 locally repackages or transcodes Matroska (.mkv) video files into the standard MP4 container for maximum device compatibility.

Yes, 100% free with no limits, no signup, and no watermarks.
No. Everything runs locally in your browser — your file never leaves your device.
Subtitles embedded in MKV are generally not remuxed; the video and audio tracks are converted.